Method and apparatus for providing conference call announcement using SIP signalling in a communication system

ABSTRACT

A method and corresponding equipment for setting up a conference call via a communication network that uses session initiation protocol (SIP) signalling for call setup, the method including steps (E 1   a  E 2   a  E 3   a  E 4   a ) of providing during the call setup signalling to a subscriber invited to participate in the conference call an indication that the call is a conference call and including in the call setup signalling a reference to a group document indicating information about the conference call, such as the other invited participants, or including the group document itself.

TECHNICAL FIELD

[0001] The present invention relates to providing additional informationduring a call setup via a communication system using SIP (SessionInitiation Protocol) signalling for call setup, and in particular, forindicating that an incoming call is a conference call, i.e. a callinvolving with more than two participants.

BACKGROUND ART

[0002] It is known in the art for a communication system (possiblyincluding one or more wireless or radio access networks) to providegroup or conference calling. It is also known in the art to use SIP(Session Initiation Protocol) to set up a call between two or more callparticipants when at least one is a subscriber to a communicationnetwork (and so communicates with the other participants over acommunication path that includes the radio access network of thecommunication network). Additionally, it is known in the art to use aSIP INVITE method (a message or in other words a communication) having aCall-Info header containing a URL (Uniform Resource Locator) referringto (a document or file providing) supplementary call information. Inaddition, a SIP INVITE method can also have an Alerting-Info headercontaining a URL referring to a ringing tone or other headers used forincluding additional information about the session (e.g. the subject tobe discussed during the call being set up). The supplementary callinformation or ringing tone must be fetched by the callee by someadditional methods, using e.g. HTTP (hypertext transfer protocol).

[0003] What the prior art does not teach, however, is for a mobilecaller to provide, as part of call set up signalling, information abouta proposed conference call, such as that the call being set up is to bea conference call and who the invited participants are. It would beadvantageous to use SIP signalling for call set up to invite subscribersreachable by an originating subscriber to participate in a group orconference call (and so to identify the call as a proposed conferencecall), and also to use SIP signalling during call set up to provideother services in connection with setting up a conference call, such asto indicate the other invited participants.

DISCLOSURE OF THE INVENTION

[0004] Accordingly, in a first aspect of the invention, a method isprovided for use by a caller terminal in setting up a conference callfor a voice call or messaging session to a callee terminal, the callerterminal subscribed to a component of a communication network includinga conference server functioning as a signaling node for the conferencecall, the communication system using session initiation protocol (SIP)signalling for call set up, the method including a step in which thecaller terminal provides according to SIP signalling a call setupcommunication to the callee terminal either via the conference server ordirectly, the method characterized in that in the step in which thecaller terminal signals to the callee terminal the call setupcommunication, the caller terminal includes in the call setupcommunication an indication that the call being set up is a conferencecall and also includes in the call setup communication either a groupdocument indicating possible participants in the conference call or areference to the group document.

[0005] In accord with the first aspect of the invention, thecommunication network may include a wireless communication component.

[0006] Also in accord with the first aspect of the invention, the methodmay also comprise a step in which the callee, upon receiving the callsetup communication, displays or otherwise provides the indication thatthe call being set up is a conference call and displays or otherwiseprovides the group document indicating possible participants in theconference call.

[0007] Also in accord with the first aspect of the invention, the callsetup communication may be a SIP INVITE or REFER communication includinga Call-info header, and the indication that the call being set up is aconference call and the group document or reference to the groupdocument may both be included in the Call-info header. Further, thecaller may send the conference server a REFER communication, and inresponse, the conference server may issue an INVITE communication to thecallee. Further still, the conference server may use a uniform resourceidentifier in a Refer-to header of the REFER communication as a basisfor determining that an INVITE communication is to be provided to thecallee. Also further, a group server may host a data store holding thegroup document and the group server may provide a uniform resourcelocator for the group document upon receiving the group document andstoring the group document in the data store, and the reference to thegroup document may be the uniform resource locator indicating the groupdocument on the group server of the communication network. Furtherstill, the group server may be a component of the conference server.Also further, the reference to the group document may be a reference toa SIP MESSAGE communication sent to the callee. Still also further, thegroup document may be included in the Call-info header as a multipartmail MIME enclosure. Even still also further, the group document may beincluded in the Call-info header as XML script.

[0008] Also in accord with the first aspect of the invention, theconference server may use the group document as a basis for determiningthat an INVITE communication is to be provided to the callee. Further,the conference server may be prompted to send an INVITE communication tothe callee and to other possible participants included in the groupdocument based on receiving an INVITE communication from the caller.Still further, the INVITE communication prompting the conference serverto send an INVITE communication to the callee and to other possibleparticipants in the group document may include a parameter value forindicating to the conference server that the conference server is tosend the INVITE communication to the callee and to the other possibleparticipants.

[0009] In a second aspect of the invention, a mobile station isprovided, comprising means for performing the steps of performed by thecaller and the callee according to the first aspect of the invention.

[0010] In a third aspect of the invention, a system is provided,comprising: a communication network using SIP signalling for call setup,and including a conference server functioning as a signalling node forenabling a conference call and also including a group server for holdingand making accessible group documents indicating members of a group, acaller terminal according to the second aspect of the invention andconnected to the communication network, and also a plurality of calleeterminals all subscribing to one or another component of thecommunication network so as to be mutually reachable via thecommunication network, wherein upon receiving a communication prefatoryto a call setup communication and including either a group document or areference to a group document, the conference server provides a callsetup communication including either the group document or the referenceto a group document.

[0011] In a fourth aspect of the invention, a conference server isprovided comprising means for performing the steps according to thefirst aspect of the invention indicated as steps performed by theconference server.

[0012] In a fifth aspect of the invention, a system is provided,comprising a conference server functioning as a signalling node forenabling a conference call and also including a group server for holdingand making accessible group documents, upon receiving a communicationprefatory to a call setup communication and including either a groupdocument or a reference to a group document, provides a call setupcommunication including either the group document or the reference to agroup document.

[0013] In a sixth aspect of the invention, a computer program product isprovided comprising: a computer readable storage structure embodyingcomputer program code thereon for execution by a computer processor in acaller terminal in setting up a conference call for a voice call ormessaging session to a callee terminal, the caller terminal subscribedto a component of a communication network including a conference serverfunctioning as a signaling node for the conference call, thecommunication system SIP signalling for call set up, with said computerprogram code comprising: computer program code for causing the computerprocessor of the caller terminal to perform a step in which the callerterminal provides according to SIP signalling a call setup communicationto the callee terminal either via the conference server or directly; thecomputer program code characterized in that in the step in which thecaller terminal signals to the callee terminal the call setupcommunication, the caller terminal includes in the call setupcommunication an indication that the call being set up is a conferencecall and also includes in the call setup communication either a groupdocument indicating possible participants in the conference call or areference to the group document.

[0014] In a seventh aspect of the invention, a computer program productis provided comprising: a computer readable storage structure embodyingcomputer program code thereon for execution by a computer processor in aconference server in communication with a caller terminal setting up aconference call for a voice call or messaging session to a calleeterminal, the caller terminal subscribed to a component of acommunication network including the conference server, the conferenceserver functioning as a signaling node for the conference call, thecommunication system using SIP signalling for call set up, with saidcomputer program code comprising: computer program code for causing thecomputer processor of the conference server to perform a step in whichthe conference server provides according to SIP signalling a call setupcommunication to the callee terminal; the computer program codecharacterized in that in the step in which the conference server signalsto the callee terminal the call setup communication, the conferenceserver includes in the call setup communication an indication that thecall being set up is a conference call and also includes in the callsetup communication either a group document indicating possibleparticipants in the conference call or a reference to the groupdocument.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of theinvention will become apparent from a consideration of the subsequentdetailed description presented in connection with accompanying drawings,in which:

[0016]FIG. 1 is a schematic illustrating scenarios in which a conferenceserver sets up a conference call between a caller and callees, accordingto each of the principal embodiments of the invention, with at least thecallees all indicated in a group document;

[0017]FIG. 2 is a schematic illustrating different mechanisms by whichthe group document is communicated between entities, such as between thecaller and the conference server;

[0018]FIG. 3 is a schematic illustrating the use of each of thecommunication mechanisms of FIG. 2 in an embodiment according to thefirst embodiment for which a scenario is illustrated in FIG. 1;

[0019]FIG. 4 is a schematic illustrating a scenario according to thefirst embodiment for which a scenario is illustrated in FIG. 1, but withthe embodiment modified to use a group invitation mechanism according tothe invention; and

[0020]FIG. 5 is another scenario according to the third embodiment forwhich a scenario is illustrated in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

[0021] The invention provides an extension to SIP call set up signallingin a 3G (Third Generation Partnership Program) wireless communicationsystem so as to indicate to a callee that an incoming call is a group(conference) call, and possibly also to indicate who the invitedparticipants are.

[0022] Referring now to FIG. 1, the invention is shown generally interms of scenarios according to four embodiments E1 E2 E3 E4, each amethod for use by a caller terminal 12 in setting up a call to a calleeterminal 16 (as one of several potential participants in a conferencecall), with the caller terminal 12 subscribed to a component of acommunication network, of which only a group server component 14 and agroup-server. 15 are shown, a communication network that uses sessioninitiation protocol (SIP) signalling for call set up. The fourembodiments E1 E2 E3 E4 each include a respective step E1 a E2 a E3 a E4a in which the caller terminal 12 signals a call setup communication tothe callee terminal 16 according generally to prior art SIP signallingbut distinguished from the prior art in that in the step E1 a E2 a E3 aE4 a in which the caller terminal 12 signals to the callee terminal 16(possibly via a conference server 14) the call setup communication, thecaller terminal 12 (or conference sever 14) includes in the call setupcommunication an indication that the call being set up is a conferencecall, and also includes in the call setup communication a reference toinformation indicating other invited participants or the informationitself.

[0023] The scenarios according to the four embodiments E1 E2 E3 E4indicated in FIG. 1 assume that the conference server 14 and the groupserver 15 are separate entities. The invention does, however, also applyin arrangements where the conference server 14 and group server arebundled together as a single entity, in which case the message flowsshown in FIG. 1 between the conference server 14 and group server 15 areinternal data flows. The conference server is a server that functions asa signalling node for conference calls; each participant in a conferencecall has an SIP dialog with the conference server (which also takes careof mixing the media streams in case of a multimedia conference). Thegroup server contains a repository of groups in a data store (notshown), i.e. a set of contacts, each identified by a group URI (uniformresource identifier), and when a group (i.e. a group document) is addedto the group server by an application, the group server returns to theapplication the URI assigned to the group.

[0024] Still referring to FIG. 1, in the scenario according toembodiment E1, in a message communication not shown, the caller terminal12 first sends an INVITE communication to the conference server 14 forsetting the resources in the network, and once the conference serverreceives the INVITE communication, the session is established betweenthe caller 12 and the conference server 14. Next, in order to initiate aconference call among members of a group, the caller terminal 12 sends aREFER communication to the conference server 14, including in the REFERcommunication what is here called a group document, i.e. a documentindicating who belongs to the group. A REFER communication/method alwayscarries a Refer-to header, which in the invention contains the URI(uniform resource identifier) to which the conference server 14 is tosend the INVITE communication. This is so because if the URI in theRefer-to header is a SIP URI, then unless another method, such as “BYE”is indicated in the Refer-to header, the recipient of the REFERcommunication sends an INVITE communication to the indicated URI.(Besides being used to send an INVITE communication to a URI, A REFERcommunication/method can also be used to eliminate a participant in aconference call by using the BYE method in the Refer-to header, as ine.g., “Refer-to: ue2@att.com;method=BYE” which results in the recipientof the REFER communication sending a BYE communication to ue2@att.com.

[0025] Upon receiving the REFER communication, the conference server 14then sends the group document to the group server 15 (assumed in thedescription that follows to be separate from the conference server 14),and can do so by various means, such as e.g. a SIP MESSAGE communicationor a HTTP/XML (hypertext transport protocol/extensible markup language)communication or a HTTP/SOAP (simple object access protocol)communication. (XML is as e.g. set out at www.w3.org/TR/REC-XML, andserves to specify a document/web page markup language, such as HTML).The group server 15 then returns to the conference server the URL forthe group document. As soon as the URL is received, the conferenceserver 14 sends an INVITE to the callee 16 (as indicated in the Refer-toheader of the REFER communication received by the conference server),and includes in the Call-info header of the INVITE the URL of the groupdocument. (As mentioned above, the REFER method/communication alwayscarries a Refer-to header, which contains the URI to which theconference server or other recipient of the REFER communication is tosend the INVITE, and in this embodiment it is the Refer-to header of theREFER communication that is used by the conference server as indicatingthe intended recipient of an INVITE communication, and not the groupdocument. (In E1 the Refer-to header contains the URI of the callee 16,and in E2 the Refer-to header contains the URI of the conference server14.) Thus, if the caller 12 in embodiment E1 wants to make a conferencecall to five persons, then (after first setting the session with theconference server by sending an INVITE communication to the conferenceserver) it issues five REFER communications, one for each person. Thegroup document is delivered in this embodiment for informationalpurposes only; it is not used in orchestrating call setup in any way.

[0026] The callee (terminal) 16, upon receiving the INVITE, reads theURL of the group document, retrieves the group document from the groupserver 15 using the URL, displays (on e.g. an LED screen) or otherwiseprovides (e.g. by speech or by some predetermined signal) an indicationthat the call being set up is a conference call and displays orotherwise provides the group document indicating the possibleparticipants in the conference call, and after the (user of the) callee(terminal) 16 inspects the group document, the callee 16 sends a SIP OKcommunication to the conference server 14, thereby completing call setup (for the callee 16).

[0027] As mentioned, each of the embodiments E1 E2 E3 E4 includes arespective step E1 a E2 a E3 a E4 a in which the caller terminal 12signals to the callee terminal 16 (possibly via a conference server 14)a call setup communication, and the caller terminal 12 (or conferencesever 14) includes in the call setup communication an indication thatthe call being set up is a conference call and also includes a reference(such as a URL or a reference to a SIP MESSAGE) to the group document(information indicating other invited participants) or includes thegroup document itself either in one header or in the body, e.g. usingMIME (Multipurpose Internet Mail Extension) multipart content. It isimportant to understand that what is shown in FIG. 1 are specificscenarios according to each of four embodiments. Actual message flowsaccording to each of the embodiments can differ in some respects fromthose shown for the scenarios illustrated in FIG. 1, or in other words,scenarios can be illustrated for each of the four embodiments withmessage flows that are different from what is shown in FIG. 3 in somerespects. What is the same for any scenario for each embodiment is themessage flow corresponding to the step E1 a E2 a E3 a E4 a in which thecaller terminal 12 signals to the callee terminal 16 (possibly via aconference server 14) a call setup communication including either areference to the group document or the group document itself. Thus, inparticular, in the embodiment E1, instead of including in the INVITEcommunication of step E1 a a URL for the group document, the groupdocument can itself be included in the INVITE communication, and thus,in such a scenario, the message flows “get group document” and “returngroup document” between the callee 16 and the group server 15 would notoccur.

[0028] Referring now to FIG. 2, various specific alternative mechanismsM1 M2 M3 M4 are indicated by which, in each of the embodiments E1 E2 E3E4, the group document may be included in the respective step E1 a E2 aE3 a E4 a in which the caller terminal 12 signals to the callee terminal16 (possibly via a conference server 14) the call setup communication.For example, and referring now also to FIG. 3, the embodiment E1(FIG. 1) is shown in four different scenarios each using a different oneof the mechanisms M1 M2 M3 M4, as indicated (using E1/M1 to indicatemechanism M1 used for embodiment E1, and so on). Thus, in the scenarioin FIG. 3 using mechanism M1, in the step E1 a in which the conferenceserver 14 sends an INVITE communication to the callee 16, the Call-infoheader of the INVITE includes (in XML script or any similar language,such as XHTML, or in any form able to be displayed directly to the user)the URL for the group document, as indicated in FIG. 2 for mechanism M1.In the scenario in FIG. 3 using mechanism M2, in the step E1 a, theCall-info header of the INVITE communication from the conference server14 includes a reference to a MESSAGE communication also sent by theconference server 14 to the callee 16, and the group document isincluded in the MESSAGE communication. (FIG. 3 shows only part of theSIP message sequence for call setup; e.g. in E1/M3, an ACK communicationis sent by the conference server 14 upon receiving the OK communicationfrom the callee 16.) In the scenario in FIG. 3 using mechanism M3, inthe step E1 a, the Call-info header of the INVITE communication from theconference server 14 includes the group document itself as a MIMEenclosure, and in the scenario using mechanism M4, the group document isincluded in the Call-info header of the INVITE communication of step E1a as XML script. (MIME refers to an official Internet standard thatspecifies how messages must be formatted so that they can be exchangedbetween different email systems; it enables communicating many types offiles or documents in an email message, including text, images, audio,video, and other application-specific data.

[0029] Referring now again to FIG. 1, in the other embodiments E2 E3 E4,in the scenarios indicated there (which are only some possiblescenarios) the caller (terminal) 12 places the group document on thegroup server 15 prefatory to the call being set up, and in response thegroup server 15 returns the URL for the group document. In placing thegroup document on the group server 15, just as in the scenario indicatedfor embodiment E1, the group document can be conveyed to the groupserver 15 using various means, such as e.g. a SIP MESSAGE communicationor a HTTP/XML communication or a HTTP/SOAP communication. Then, in theE2 scenario, in the step E2 a setting up the conference call, the callerterminal 12 sends the callee 16 a REFER communication including the URLof the group document. When the callee 16 receives the REFERcommunication, it uses the URL included in the Call-info header toretrieve the group document, and it then displays the list ofparticipants to the user of the callee (terminal) 16. The user, upondeciding to participate in the conference call, has the callee 16 send aSIP INVITE communication to the conference server 14, to which theconference server responds with a SIP OK, thus completing the call setup(for the callee 16).

[0030] Still referring to FIG. 1, in the E3 scenario, after placing thegroup document on the group server 15, the caller 12 sends a SIPcommunication to the conference server 14 indicating a scheduled timeand date for a conference call with the members of the group indicatedby the group document, and includes in the communication the URL of thegroup document. In the E3 embodiment, unlike in the other embodiments,the conference server will, at the scheduled time, send an INVITEcommunication to each URI indicated in the group document, the groupdocument preferably includes the URI of the caller too, not only theURIs of the callees. (It is of course also possible that the conferenceserver can be made to send the INVITE communication to the caller at thescheduled time using some other mechanism, such as e.g. adding thecaller to the group document if the caller is not already included, whenthe conference server first receives the group document from thecaller.) Also, it should be understood that the E3 embodiment differsfrom the E1, E2 and E4 embodiments in that the conference call isultimately initiated based on only a single communication from thecaller to the conference server, namely the initial communication in themessage sequence diagram of FIG. 1 from the caller to the conferenceserver, the communication providing the scheduled time and the groupdocument or its URL. In the other embodiments, the caller sends a REFERcommunication to the conference server for each callee, since it is theRefer-to header in the REFER communication that prompts the conferenceserver to send INVITE communication to the callees in the otherembodiments.

[0031] Still referring to the scenario for the E3 embodiment as shown inFIG. 1, the communication sent from the caller 12 first to theconference server 14 is an SIP communication/method, although not anINVITE communication, but instead a communication such as MESSAGE orPUBLISH, and includes the group document or its URL and also includes afurther parameter indicating that INVITE communications are to be sentto the participants indicated in the group document, but only at ascheduled time as indicated by a calendar event included in the SIPcommunication. In indicating a scheduled time and date for theconference call, vCalendar or some other non-real-time schedulingmechanism can be used. In case of using specifically vCalendar, asopposed to some other non-real-time invitation (i.e. scheduling)mechanism, the notification that a conference call is being set up isprovided as what is called an event including a piece of data indicatingthat a conference call is scheduled for some future time and date. TheURL for the group document can be included in the communication as partof the event or separate from it. (vCalendar is an open specificationproviding an exchange format for personal scheduling information, ableto be used in exchanging information across a broad range of transportmethods.) At the scheduled time and date, the conference server 14 sendsto the callee 16 (and also to the other callees, as well as to thecaller) and INVITE communication including in the Call-info header theURL of the group document. The scenario then proceeds as in the E1scenario (with the callee retrieving the group document from the groupserver 15, examining it, and responding to the conference server 14 witha SIP OK, thereby completing call setup). (Another scenario according tothe E3 embodiment is indicated in FIG. 5 and described below.)

[0032] Still referring to FIG. 1, in the E4 scenario, after placing thegroup document on the group server 15, the caller 12 sends a REFERcommunication to the conference server 14 and includes in the Call-infoheader of the REFER communication the URL of the group. The conferenceserver then retrieves the group document (in message flows not shown),determines that callee 16 is a member of the group, and sends the callee16 a INVITE communication, including in the Call-info header of theINVITE communication the URL of the group document. The scenario thenproceeds as in the E1 scenario.

[0033] The invention thus comprehends four embodiments E1 E2 E3 E4 (FIG.1), each allowing up to four mechanisms M1 M2 M3 M4 (FIG. 2) by whichthe callee 16 obtains the group document. When mechanisms M2 (separateMESSAGE) M3 (MIME) or M4 (XML script) are used, there are no messageflows to or from the group server 15, and so in case of using themechanisms M2 M3 M4 not making use of a URL for the group document,embodiment E4 is the same as embodiment E1.

[0034] Referring now to FIG. 4, the invention also comprehends anembodiment E1′ (corresponding to embodiment E1 FIG. 1), an embodiment inwhich the conference server uses the group document as the basis fordetermining the URI's to which it is to issue an INVITE communication.In the embodiment E1′, the caller 12 sends an INVITE communicationcarrying the group document to the conference server 14, which examinesthe group document and then issues INVITE communications to all membersin the group document (except the caller 14), in what amounts to a“group INVITE” mechanism. In some embodiments using the group INVITEmechanism of the invention, the INVITE communication would use a newparameter value for what is called the Content-Disposition header (or asimilar SIP header), a value such as “initiate-conference” or somesimilar token that is used for requesting that the conference serveritself initiate an action using information included in the body of thecommunication or in some other header; the parameter value (such as“initiate-conference”) would thus be used to indicate to the conferenceserver that the conference server is to initiate the conferencingitself, using the information in the group document or requesting theparticipant URIs from the group server 15. Such embodiments savebandwidth by avoiding having the caller send a REFER communication tothe conference server for each participant.

[0035] Still referring to FIG. 4, in embodiment E1′ (embodiment E1modified to use the group INVITE mechanism), the caller 12 first sendsan INVITE communication to the conference server 14, and includes in theINVITE communication the group document (or its URL), and possibly alsoincludes the new “initiate-conference” parameter value. (The groupINVITE mechanism could also be used in embodiment E4 of FIG. 1, butsince in using the group INVITE mechanism the group document is providedto the conference server 14 by the caller using the group INVITE,modifying embodiment E4 to use the group INVITE would result inembodiment E1′, already described above.)

[0036] Referring now to FIG. 5, embodiment E3 is shown according toanother scenario, differing from the scenario illustrated for embodimentE3 in FIG. 1. Recall that embodiment E3 provides for scheduling aconference call at some future time and date, and the caller 12 needsend only a single initial communication to the conference server 14(namely the communication providing the group document and the scheduledtime and date) to have the conference server, at the scheduled time,initiate the conference call. In the scenario for E3 shown in FIG. 5,the caller 12 first sends the conference server 14 an SIP MESSAGEincluding the group document, and the conference server then sends thegroup document to the group server 15, which, in response, sends to theconference server the URL for the group document as well as the URIs foreach (potential, i.e. to-be-invited participant). In the scenario here,it is the group server 15 that parses the group document so as todetermine the URIs for each participant, although it is of coursepossible to have the conference server do so, in which case the groupserver would not need to return the URIs for the participants, but onlythe URL for the group document. When the conference server receives theURIs, (in an optional step) it sends a MESSAGE to each callee (callee1,callee2, . . . ) including the URL of the group document and alsoincluding the calendar event so that the participant can, if desired,add the conference call to the callee's schedule. In the scenario here,a third callee, callee3, upon receiving the scheduling MESSAGE, isassumed to have viewed the group document and decided not to participate(which it can do by either removing its name from the group document onthe group server) or by sending a SIP communication to the conferenceserver, such as a SIP “402 Busy Here” communication. At the scheduledtime, the conference server initiates the conference call by sending toeach participant (caller and callees, but not callee3) an INVITEcommunication including the group document URL. Thus, a step E3 a isperformed, corresponding to the steps E1 a E2 a E4 a of the otherembodiments, in which the call setup communication (an INVITEcommunication from the conference server to the callee) is signalledincluding an indication that the call being set up is a conference calland also including in the call setup communication either the groupdocument indicating possible participants in the conference call or areference to the group document.

[0037] It should be understood that the call set up described and shownin the various embodiments above can be a call set up for either a voicecall or for a messaging session, such as a co-called instant messagingsession, in which parties exchange text or graphics (or both) inreal-time, i.e. so that the messages are provided to the otherparticipants in the conference call substantially without delay.

[0038] It is to be understood also that the above-described arrangementsare only illustrative of the application of the principles of thepresent invention. In particular, it should be understood that theinvention is of use in any communication network that uses SIPsignalling for call setup, not necessarily only wireless communicationsystems that use SIP signalling. Numerous modifications and alternativearrangements may be devised by those skilled in the art withoutdeparting from the scope of the present invention, and the appendedclaims are intended to cover such modifications and arrangements.

What is claimed is:
 1. A method for use by a caller terminal (12) insetting up a conference call for a voice call or messaging session to acallee terminal (16), the caller terminal (12) subscribed to a componentof a communication network including a conference server (14)functioning as a signaling node for the conference call, thecommunication system (15) using session initiation protocol (SIP)signalling for call set up, the method including a step (E1 a E2 a E3 aE4 a) in which the caller terminal (12) provides according to SIPsignalling a call setup communication to the callee terminal (16) eithervia the conference server (14) or directly, the method characterized inthat in the step (E1 a E2 a E3 a E4 a) in which the caller terminal (12)signals to the callee terminal (16) the call setup communication, thecaller terminal (12) includes in the call setup communication anindication that the call being set up is a conference call and alsoincludes in the call setup communication either a group documentindicating possible participants in the conference call or a referenceto the group document.
 2. The method of claim 1, wherein thecommunication network includes a wireless communication component. 3.The method of claim 1, further comprising the step in which the callee(16), upon receiving the call setup communication, displays or otherwiseprovides the indication that the call being set up is a conference calland displays or otherwise provides the group document indicatingpossible participants in the conference call.
 4. The method of claim 1,wherein the call setup communication is a SIP INVITE or REFERcommunication including a Call-info header, and the indication that thecall being set up is a conference call and the group document orreference to the group document are both included in the Call-infoheader.
 5. The method of claim 4, wherein the caller (12) sends theconference server (14) a REFER communication, and in response, theconference server (14) issues an INVITE communication to the callee(16).
 6. The method of claim 5, wherein the conference server (14) usesa uniform resource identifier in a Refer-to header of the REFERcommunication as a basis for determining that an INVITE communication isto be provided to the callee (16).
 7. The method of claim 4, wherein agroup server (15) hosts a data store holding the group document and thegroup server (15) provides a uniform resource locator for the groupdocument upon receiving the group document and storing the groupdocument in the data store, and wherein the reference to the groupdocument is the uniform resource locator indicating the group documenton the group server (15) of the communication network (15).
 8. Themethod of claim 7, wherein the group server (15) is a component of theconference server (14).
 9. The method of claim 4, wherein the referenceto the group document is a reference to a SIP MESSAGE communication sentto the callee (16).
 10. The method of claim 4, wherein the groupdocument is included in the Call-info header as a multipart mail MIMEenclosure.
 11. The method of claim 4, wherein the group document isincluded in the Call-info header as XML script.
 12. The method of claim1, wherein the conference server (14) uses the group document as a basisfor determining that an INVITE communication is to be provided to thecallee (16).
 13. The method of claim 12, wherein the conference server(14) is prompted to send an INVITE communication to the callee (16) andto other possible participants included in the group document based onreceiving an INVITE communication from the caller (12).
 14. The methodof claim 13, wherein the INVITE communication prompting the conferenceserver (14) to send an INVITE communication to the callee (16) and toother possible participants in the group document includes a parametervalue for indicating to the conference server (14) that the conferenceserver is to send the INVITE communication to the callee (16) and to theother possible participants.
 15. A mobile station, comprising means forperforming the steps of claim 3 indicated as steps performed by thecaller (12) and the callee (16).
 16. A system, comprising: acommunication network using session initiation protocol (SIP) signallingfor call setup, and including a conference server (14) functioning as asignalling node for enabling a conference call and also including agroup server (15) for holding and making accessible group documentsindicating members of a group, a caller terminal (12) as in claim 15 andconnected to the communication network, and also a plurality of calleeterminals (16) all subscribing to one or another component of thecommunication network so as to be mutually reachable via thecommunication network, wherein upon receiving a communication prefatoryto a call setup communication (E1 a E2 a E3 a E4 a) and including eithera group document or a reference to a group document, the conferenceserver (14) provides a call setup communication (E1 a E3 a E4 a)including either the group document or the reference to a groupdocument.
 17. A conference server, comprising means for performing thesteps of claim 1 indicated as steps performed by the conference server(14).
 18. A system, comprising a conference server (14) functioning as asignalling node for enabling a conference call and also including agroup server (15) for holding and making accessible group documentsindicating members of a group, wherein the conference server (14), uponreceiving a communication prefatory to a call setup communication (E1 aE2 a E3 a E4 a) and including either a group document or a reference toa group document, provides a call setup communication (E1 a E3 a E4 a)including either the group document or the reference to a groupdocument.
 19. A computer program product comprising: a computer readablestorage structure embodying computer program code thereon for executionby a computer processor in a caller terminal (12) in setting up aconference call for a voice call or messaging session to a calleeterminal (16), the caller terminal (12) subscribed to a component of acommunication network including a conference server (14) functioning asa signaling node for the conference call, the communication system (15)using session initiation protocol (SIP) signalling for call set up, withsaid computer program code comprising: computer program code for causingthe computer processor of the caller terminal (12) to perform a step (E1a E2 a E3 a E4 a) in which the caller terminal (12) provides accordingto SIP signalling a call setup communication to the callee terminal (16)either via the conference server (14) or directly; the computer programcode characterized in that in the step (E1 a E2 a E3 a E4 a) in whichthe caller terminal (12) signals to the callee terminal (16) the callsetup communication, the caller terminal (12) includes in the call setupcommunication an indication that the call being set up is a conferencecall and also includes in the call setup communication either a groupdocument indicating possible participants in the conference call or areference to the group document.
 20. A computer program productcomprising: a computer readable storage structure embodying computerprogram code thereon for execution by a computer processor in aconference server (14) in communication with a caller terminal (12)setting up a conference call for a voice call or messaging session to acallee terminal (16), the caller terminal (12) subscribed to a componentof a communication network including the conference server (14), theconference server (14) functioning as a signaling node for theconference call, the communication system (15) using session initiationprotocol (SIP) signalling for call set up, with said computer programcode comprising: computer program code for causing the computerprocessor of the conference server (14) to perform a step (E1 a E3 a E4a) in which the conference server (14) provides according to SIPsignalling a call setup communication to the callee terminal (16); thecomputer program code characterized in that in the step (E1 a E3 a E4 a)in which the conference server (14) signals to the callee terminal (16)the call setup communication, the conference server (14) includes in thecall setup communication an indication that the call being set up is aconference call and also includes in the call setup communication eithera group document indicating possible participants in the conference callor a reference to the group document.